A coating material based on acetic anhydride blend modification and a preparation method thereof

Abstract

The application discloses a coating material based on acetic anhydride blending modification and a preparation method thereof, and comprises the following steps: S1, weighing a certain amount of polyvinyl alcohol solid and dissolving the polyvinyl alcohol solid in a mixed solution of acetic anhydride and water to obtain a polyvinyl alcohol solution; S2, adding the mixed solution of acetic anhydride and water to the prepared polyvinyl alcohol solution and adding hydrochloric acid as a catalyst; S3, then stirring and reacting in a water bath heating environment, and obtaining a PVA-Ac2O coating liquid after natural cooling; and S4, uniformly coating the obtained PVA-Ac2O coating liquid on a paper surface to obtain a coating material. By grafting and crosslinking PVA and acetic anhydride, acyl groups, amino groups and other related groups are introduced into the PVA molecular chain, so that the hydrophilic groups of PVA are masked. The strength performance is improved, and the barrier performance is enhanced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coating materials, and particularly relates to a coating material based on acetic anhydride blending modification and a preparation method thereof. BACKGROUND

[0002] Barrier property is a property of preventing the penetration of gas and heat, the transmission of light, maintaining the stability of the internal environment of the material, thereby prolonging the shelf life of the product. Barrier materials have been widely used in food packaging, medicine and health, electronic equipment, chemical industry and other fields due to their excellent barrier properties, and also have good application prospects and development space.

[0003] At present, the high polymer material with a thickness of 25.4 μm, a temperature of 22.8℃, an oxygen transmission rate of 194 x 10 -5 cm 3 ·20 μm / m 2 ·d·Pa below is called a barrier material. The high barrier materials most widely used at present and having industrial production prospects mainly include ethylene-vinyl alcohol copolymer, polyvinylidene chloride, polyamide, polyvinyl alcohol, nitrile-based resin, etc.

[0004] PVA is a common water-soluble polymer material, which has been widely used in the fields of textiles, food, papermaking, medical treatment, packaging, etc. due to its good compatibility and mechanical properties. However, the application field of PVA film is also limited to a certain extent due to the poor mechanical properties and poor water resistance of PVA film caused by the large number of hydroxyl groups in the PVA molecule.

[0005] In Chinese Patent Application No. CN 116323197 A, a cellulose product coated with polyvinyl alcohol is disclosed, comprising the following steps: providing a cellulose substrate; melting a polyvinyl alcohol polymer, wherein the hydrolysis degree of the polyvinyl alcohol polymer is 90% or higher and the melting point is in the range of 180℃ to 225℃; extruding the melted polyvinyl alcohol polymer to form a melted polyvinyl alcohol polymer film; directly applying the melted film to the surface of the substrate; and solidifying the film on the surface to form a coated material. Although the scheme discloses a melted polyvinyl alcohol polymer, the strength performance and barrier performance of the coated material are not significantly changed. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application aims to provide a coating material based on acetic anhydride blending modification and a preparation method thereof, which solves the above technical problems existing in the prior art.

[0007] The object of the present application can be achieved by the following technical solutions:

[0008] The application discloses a coating material based on acetic anhydride blending modification, which comprises the following steps: adding 1-6% of polyvinyl alcohol into acetic anhyydride / water mixed solution, introducing acyl, amino and other related groups into the PVA molecular chain, achieving the effect of masking the hydrophilic group of polyvinyl alcohol, obtaining PVA-Ac2O coating liquid, and uniformly coating the PVA-Ac2O coating liquid on the surface of paper to form a coating isolation material.

[0009] The obtained coating isolation material has the following properties: air permeability is 1.06 um·pa -1 ·s -1 Cobb value is 19.84 g·m -2 Tensile index is 24.8 N·m·g -1 Water contact angle is 97.5°, and the coating material is hydrophobic; oil contact angle is 97.4°, and the coating material has a fat resistance grade of 8.

[0010] Further, the polyvinyl alcohol is added into the acetic anhydride / water mixed solution in a weight ratio of 4% to obtain the PVA-Ac2O coating liquid.

[0011] The application further discloses a preparation method of the coating material based on acetic anhydride blending modification.

[0012] S1, weighing a certain amount of polyvinyl alcohol solid and dissolving the polyvinyl alcohol in an acetic anhydride / water mixed solution to obtain a polyvinyl alcohol solution;

[0013] S2, adding the acetic anhydride / water mixed solution to the prepared polyvinyl alcohol solution and adding hydrochloric acid as a catalyst;

[0014] S3, then stirring and reacting in a water bath heating environment, and naturally cooling to obtain the PVA-Ac2O coating liquid;

[0015] S4, uniformly coating the obtained PVA-Ac2O coating liquid on the surface of paper to obtain the coating material.

[0016] Further, in S1, the acetylation degree of the polyvinyl alcohol is controlled by adjusting the proportion of water and acetic anhydride.

[0017] Further, in S3, the reaction is carried out in a water bath heating environment at 20-90 DEG C.

[0018] Further, in S3, the reaction is carried out in a water bath heating environment at 65 DEG C.

[0019] Further, in S3, the water bath heating reaction time is 3h.

[0020] Further, in S4, after the obtained PVA-Ac2O coating liquid is uniformly coated on the surface of paper, the paper is naturally dried, then pressed at 76 DEG C and dried for 10 min, and then placed in a constant temperature and humidity laboratory for more than 12 hours to balance the moisture.

[0021] The beneficial effects of the present application are as follows:

[0022] 1、The urea in the present application is modified, and the related acyl group, amino group and other groups successfully graft and hydrogen bond crosslink with PVA; after acetylation modification, the hydroxyl group on the PVA molecule is replaced by acyl group, and the modified PVA infrared spectrum appears a characteristic peak that does not exist in the original PVA spectrum. As shown in the scanning electron microscope result graph, the surface of the modified PVA barrier paper is relatively smooth, the dissolution amount of the fiber is more, the binding force between the fibers is stronger, and the void is smaller, so that the barrier property of the paper is improved.

[0023] 2、The PVA-Ac2O4% barrier paper and the PVA-Urae150mg barrier paper provided by the present application both have better barrier performance and strength performance. The air permeability of the PVA-Ac2O4% barrier paper is 1.06um·pa -1 ·s -1 , the Cobb value is 19.84g·m -2 , which is reduced by 66.1% and 74.8% compared with the original paper; the tensile index is 24.8N·m·g -1 , which is increased by 34.0% compared with the original paper; the water contact angle is 97.5°, which is hydrophobic, the oil contact angle is 97.4°, and the fat resistance grade is 8, which is obviously improved compared with the original paper. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below.

[0025] Figure 1 is the ESM graph of various barrier papers of the embodiments of the present application;

[0026] Figure 2 is the FT-IR graph of PVA and modified PVA of the embodiments of the present application;

[0027] Figure 3 is the tensile index graph of the barrier paper of the embodiments of the present application;

[0028] Figure 4 is the water contact angle ESM graph of the barrier paper of the embodiments of the present application;

[0029] Figure 5 is the oil contact angle ESM graph of the barrier paper of the embodiments of the present application;

[0030] Figure 6 is the air permeability schematic diagram of the barrier paper of the embodiments of the present application;

[0031] Figure 7Cobb test schematic diagram of the barrier paper of the embodiment of the present application;

[0032] Figure 8 Influence schematic diagram of various Ac2O addition amounts on paper grease resistance grade of the embodiment of the present application;

[0033] Figure 9 Influence schematic diagram of different modification temperatures on paper grease resistance grade of the embodiment of the present application;

[0034] Figure 10 Paper grease resistance grade test diagram of the embodiment of the present application. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the drawings of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0036] The embodiment of the present application provides a coating material based on acetic anhydride blending modification, including adding 4% of polyvinyl alcohol by weight into an acetic anhydride / water mixture, introducing acyl, amino and other related groups into the PVA molecular chain, achieving the effect of masking the hydrophilic groups of polyvinyl alcohol, obtaining PVA-Ac2O coating liquid, and uniformly coating on the surface of paper to form a coating isolation material.

[0037] The obtained coating isolation material has an air permeability of 1.06um·pa -1 ·s -1 , a Cobb value of 19.84g·m -2 , a tensile index of 24.8N·m·g -1 , a water contact angle of 97.5°, a hydrophobic property, an oily contact angle of 97.4°, and a grease resistance grade of 8.

[0038] The preparation method of the coating material based on acetic anhydride blending modification includes the following steps:

[0039] S1, weighing a certain amount of polyvinyl alcohol solid and dissolving it in an acetic anhydride / water mixture to obtain a polyvinyl alcohol solution; the acetylation degree of polyvinyl alcohol is controlled by adjusting the ratio of water and acetic anhydride.

[0040] S2, adding an acetic anhydride / water mixture to the prepared polyvinyl alcohol solution and heating hydrochloric acid as a catalyst;

[0041] S3, then stirring and reacting for 3h under the condition of water bath heating at 65℃, and obtaining PVA-Ac2O coating liquid after natural cooling;

[0042] S4. After the obtained PVA-Ac2O coating solution is evenly coated on the paper surface, it is allowed to air dry naturally. Then, the paper sample is pressed and dried at 76℃ for 10 minutes, and then placed in a constant temperature and humidity laboratory for more than 12 hours to balance the moisture.

[0043] Specific plan:

[0044] 5g of PVA (1799) solid was weighed into a beaker and dissolved in 95mL of a mixture of acetic anhydride and water (acetic anhydride mass percentages were 1%, 2%, 3%, 4%, 5%, and 6%, respectively). 1mL of 5mol / L hydrochloric acid was added as a catalyst, and the degree of PVA acetylation was controlled by adjusting the ratio of water to acetic anhydride. The reaction was carried out in a magnetically stirred water bath at 65℃ and 800rpm for three hours, and after natural cooling, a PVA-Ac2O coating solution was obtained. Using the same synthesis method, PVA-Ac2O coating solutions were prepared at room temperature (25℃) and high temperature (90℃) by adjusting the reaction temperature.

[0045] The quantitative value was 70.3 g / m 2 Using A4 copy paper as the base paper, 3 mL of PVA-Ac2O was drawn using a dropper and evenly coated onto the paper surface using a self-made XT-300 coating machine to prepare PVA-Ac2O barrier paper. The paper was then air-dried at room temperature. After the reagent on the paper surface dried, it was placed on a paperboard dryer and pressed and dried at 76°C for 10 minutes. After thorough drying, the paper was placed in a constant temperature and humidity laboratory for at least 12 hours to equilibrate the moisture. Unmodified PVA (1799) and Kuraray PVA (3010) barrier papers were prepared using the same method.

[0046] FI-TR plot analysis

[0047] like Figure 2 As shown, an appropriate amount of PVA coating solution was dropped onto a dry petri dish. After coating, the film was allowed to dry naturally and then placed in a vacuum drying oven at 60°C for 12 hours. The resulting film was then tested in FI-TR.

[0048] Figure 2 The image shows the infrared spectra of PVA fibrils and Ac2O-modified PVA at different mass ratios. According to the spectra, PVA and PVA-AcO show a common wavelength at 3261.86 cm⁻¹. -1 2926.70cm -1 1420.8cm -1 and 1084.33cm -1 The same characteristic absorption peak is present at all locations. Among them, the peak at 3261.86 cm⁻¹ is particularly prominent. -1 This corresponds to the stretching vibration absorption peak of the -OH group; 2926.70 cm⁻¹ -1and 1420.8 cm -1 are the absorption peaks of symmetric stretching and asymmetric bending vibration of -CH2, respectively; and the peak at 1084.33 cm -1 is the stretching vibration peak of C-O bond. Compared with PVA fibrils, PVA-Ac2O appears a C=O stretching vibration peak at 1705.76 cm -1 which does not exist in PVA, and the stretching vibration peak of C=O is enhanced to different degrees with the addition of Ac2O, which also indicates that part of -OH in PVA is replaced by carbonyl, and PVA is successfully acetylated.

[0049] The surface morphology of the modified and unmodified PVA barrier paper was observed using a field emission scanning electron microscope, and the test results are shown in Figure 1 Figure 1 (a) can be seen, the unmodified PVA barrier paper has more PVA particles coagulated on the surface, the paper surface is rough, and the inter-fiber gap is large. From Figure 1 (c) can be seen, the urea modified and acetylated PVA barrier paper has a smoother surface, more dissolved fibers, stronger inter-fiber bonding, and smaller voids, so the barrier property of the paper is stronger.

[0050] As shown in Figure 3 , the tensile strength of the barrier paper was tested, (a) the tensile index of the acetic anhydride modified PVA coated barrier paper; (b) the tensile index of the urea grafted modified PVA coated barrier paper. The tensile index of the original paper is 18.5 N·m·g -1 , and the tensile indexes of PVA1799 and Kuraray PVA3010 barrier papers are 20.3 N·m·g -1 and 22.0 N·m·g -1 , respectively, which are 9.7% and 18.9% higher than the original paper. In the acetylation modification, when the addition amount of Ac2O is 4%, the tensile index of the paper is 24.8 N·m·g -1 , which has the best strength performance, which is 34.0% higher than the original paper; when the modifier is added in excess, the tensile performance of the paper will be slightly reduced, because the excess Ac2O increases the number of ester bonds formed between PVA and Ac2O, which will weaken the bonding force between the fibers of the paper, thereby causing the performance of the paper to decrease. In summary, the best addition amount of Ac2O in acetylation modification is 4%.

[0051] As shown in Figure 4 ​The hydrophobicity and oleophobicity of the barrier papers were tested by contact angle test, wherein: (a) base paper, (b) 1799, (c) 3010, (d) 4% acetylation modified 1799, (e) 150 mg urea grafting modified 1799.

[0052] The Wca of the base paper was only 88.6°, and the Wca of the PVA 1799 coated paper and the Kuraray PVA 3010 coated paper was 91.9° and 92.7°, respectively, which was only increased by 4.6% compared with the base paper. With the addition of the modifier, the hydrophobicity of the paper was improved to different degrees. In the acetylation modification, when the amount of Ac2O added was 4%, the Wca of the PVA-Ac2O 4% barrier paper was 92.7°, which was the highest, and was increased by 10% compared with the base paper.

[0053] Figure 5 The oil contact angle of the paper was tested, wherein: (a) base paper, (b) 1799, (c) 3010, (d) 4% acetylation modified 1799, (e) 150 mg urea grafting modified 1799.

[0054] At this time, the contact angle of the base paper was 87.8°, and the contact angle of the PVA 1799 and the Kuraray PVA 3010 was 85.4 and 87.9, respectively, and the fat resistance was not improved. The contact angle of the PVA-Ac2O 4% barrier paper was 97.4° and 93.9°, and the fat resistance was increased by 9.9% and 6.6% compared with the base paper. In summary, the PVA-Ac2O 4% barrier paper has good hydrophobicity and oil resistance.

[0055] As shown in Figure 6 The air permeability of the paper was tested, wherein: (a) air permeability of acetic anhydride modified PVA, (b) air permeability of urea grafting modified PVA.

[0056] The air permeability of the base paper was 3.13 um·pa -1 ·s -1 , and the air permeability of the PVA 1799 and the Kuraray PVA 3010 barrier paper was 1.39 um·pa -1 ·s -1 and 1.34 um·pa -1 ·s -1 , which was reduced by 55.6% and 57.1% compared with the base paper. In the acetylation modification, the air permeability of the PVA-Ac2O 4% barrier paper was the lowest, only 1.06 um·pa -1 ·s -1 , which was reduced by 66.1% compared with the base paper.

[0057] For the PVA modification optimal temperature and paper barrier, as Figure 7 shown, the Cobb value of the base paper is 79.98 g·m -2 -2, the Cobb value of the PVA1799 and Kolon PVA3010 barrier paper is 25.21 g·m -2 -2, 24.57 g·m -2 -2, the fat absorption of the barrier paper is reduced by 68.1%, 68.8% compared with the base paper. When acetylated modification, the Cobb value of the PVA-Ac2O4% barrier paper is 19.84 g·m -2 -2, and the fat absorption is reduced by 74.8% compared with the base paper. Through the study of changing the PVA modification temperature, it is found that when the PVA-Ac2O4% modification temperature is 65℃, the fat resistance of the coated barrier paper is optimal.

[0058] As shown in Figure 8 , Figure 9 , Figure 10 , the fat resistance grade of the base paper is 1, and the fat resistance grade of the PVA1799 and Kolon PVA3010 is 3 and 4, which is higher than that of the base paper. With the increase of the modifier, the fat resistance grade gradually increases, and the fat resistance grade of the PVA-Ac2O4% barrier paper in acetylated modification is 9. Through the study of changing the PVA modification temperature, it is found that when the PVA-Ac2O4% modification temperature is 65℃, the fat resistance grade of the coated barrier paper is the highest.

[0059] In summary, when the Ac2O addition amount is 4% and the reaction temperature is 65℃ in acetylated modification, the PVA-Ac2O4% barrier paper has the optimal performance.

[0060] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A method for producing a coating material based on acetic anhydride blend modification, characterized by, The method comprises the following steps: S1, weighing a certain amount of polyvinyl alcohol solid and dissolving it in a mixed solution of acetic anhydride / water to obtain a polyvinyl alcohol solution; S2, adding a mixed solution of acetic anhydride / water to the prepared polyvinyl alcohol solution and heating hydrochloric acid as a catalyst; S3, then stirring the reaction in a water bath heating environment, and obtaining a PVA-Ac2O coating solution after natural cooling; S4, uniformly coating the obtained PVA-Ac2O coating solution on the surface of paper to prepare a coating material; Wherein: adding 1-6% of polyvinyl alcohol by weight in a mixed solution of acetic anhydride / water introduces acyl and amino related groups onto the PVA molecular chain, achieves the effect of masking the hydrophilic groups of polyvinyl alcohol, obtains a PVA-Ac2O coating solution, and uniformly coats it on the surface of paper to form a coating isolation material; The obtained coated release material has an air permeability of 1.06 um·pa -1 ·s -1 ; a Cobb value of 19.84 g·m -2 ; a tensile index of 24.8 N·m·g -1 ; a water contact angle of 97.5°, being hydrophobic, an oil contact angle of 97.4°, and a fat resistance grade of 8.

2. The method for preparing a coating material based on acetic anhydride blend modification according to claim 1, characterized by, The PVA-Ac2O coating solution is obtained by adding 4% of polyvinyl alcohol by weight in a mixed solution of acetic anhydride / water.

3. The method for preparing a coating material based on acetic anhydride blend modification according to claim 1, characterized by, In S1, the acetylation degree of polyvinyl alcohol is controlled by adjusting the ratio of water and acetic anhydride.

4. The method for preparing a coating material based on acetic anhydride blend modification according to claim 1, characterized by, In S3, the reaction is carried out in a water bath heating environment of 20-90℃.

5. The method for preparing a coating material based on acetic anhydride blend modification according to claim 4, characterized by, In S3, the reaction is carried out in a water bath heating environment of 65℃.

6. The method for preparing a coating material based on acetic anhydride blend modification according to claim 5, characterized by, In S3, the water bath heating reaction time is 3h.

7. The method for preparing a coating material based on acetic anhydride blend modification according to claim 1, characterized by, In S4, after the obtained PVA-Ac2O coating solution is uniformly coated on the surface of paper, it is naturally air-dried, then pressed at 76℃ and dried for 10 min, and then placed in a constant temperature and humidity laboratory for more than 12 hours to balance the moisture.

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